In-plane switching mode liquid crystal display device and method of fabricating the same

ABSTRACT

An array substrate is provided for an in-plane switching mode liquid crystal display device. The array substrate includes a substrate, a thin film transistor on the substrate, a gate line connected to the transistor, a data line crossing the gate line and connected to the transistor such that the crossed data line and gate line define boundaries of a pixel region, a pixel electrode disposed in the pixel region connected to the transistor, and a common electrode disposed in the pixel region. The pixel electrode has at least one vertical portion and a plurality of horizontal portions, and the common electrode has at least two horizontal portions and a plurality of horizontal portions. The vertical portion of the pixel electrode is between the vertical portions of the common electrode, and the horizontal portions of the common electrode cross the vertical portion of the pixel electrode.

[0001] The present invention claims the benefit of Korean PatentApplication No. 2003-37910, filed in Korea on Jun. 12, 2003, which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a liquid crystal display device,and more particularly, to an in-plane switching mode liquid crystaldisplay device having high aperture ratio, wide viewing angle and highbrightness.

[0004] 2. Discussion of the Related Art

[0005] A liquid crystal display device uses the optical anisotropy andpolarization properties of liquid crystal molecules to produce an image.The long thin shapes of the liquid crystal molecules can be aligned tohave an orientation in a specific direction. The alignment direction ofthe liquid crystal molecules can be controlled by an applied electricfield. In other words, as an applied electric field changes, thealignment of the liquid crystal molecules also changes. Due to theoptical anisotropy of the liquid crystal molecules, the refraction ofincident light depends on the alignment direction of the liquid crystalmolecules. Thus, by properly controlling an electric field applied to agroup of liquid crystal molecules in respective pixels, a desired imagecan be produced by diffracting light.

[0006] There are many types liquid crystal displays (LCDs). One type ofLCD is an active matrix LCD (AM-LCD) that has a matrix of pixels. Eachof the pixels in an AM-LCD has a thin film transistor (TFT) and pixelelectrode. AM-LCDs are the subject of significant research anddevelopment because of their high resolution and superiority indisplaying moving images.

[0007] A related art LCD includes a color filter substrate (uppersubstrate) having a common electrode, an array substrate (lowersubstrate) having a pixel electrode, and a liquid crystal layerinterposed between the color filter substrate and the array substrate.In the related art LCD, the liquid crystal layer is driven by a verticalelectric field between the pixel electrode and the common electrode.Accordingly, the related art LCD has increased transmittance andaperture ratio. The related art LCD, however, has a narrow viewing anglebecause it is driven by the vertical electric field. To solve the aboveproblems, various types of LCDs having a wide viewing angle such as anin-plane switching (IPS) mode LCD device have been suggested.

[0008]FIG. 1 is a schematic cross-sectional view of an in-plane modeliquid crystal display device according to the related art. In FIG. 1,an in-plane switching (IPS) mode liquid crystal display (LCD) deviceincludes first and second substrates 50 and 30 facing and spaced apartfrom each other, and a liquid crystal layer 90 interposed therebetween.The first substrate 50 has a plurality of pixel regions “P₁” and “P₂.” Athin film transistor (TFT) “T,” a common electrode 58 and a pixelelectrode 72 are formed on the first substrate 50 in each pixel region“P₁” and “P₂.” The TFT “T” includes a gate electrode 52, a semiconductorlayer 62 over the gate electrode 52, a source electrode 64 and a drainelectrode 66 spaced apart from the source electrode 64. A gateinsulating layer 60 is interposed between the gate electrode 52 and thesemiconductor layer 62. The common electrode 58 and the pixel electrode72 are parallel to and spaced apart from each other.

[0009] The common electrode 58 may be formed of the same material andthe same layer as the gate electrode 52, and the pixel electrode 72 maybe formed of the same material and the same layer as the source anddrain electrodes 64 and 66. In addition, the pixel electrode 72 may beformed of a transparent material to increase aperture ratio. Even thoughnot shown in FIG. 1, a gate line, a data line crossing the gate line anda common line supplying a common voltage to the common electrode 58 maybe formed on the first substrate 50.

[0010] A black matrix 32 corresponding to the gate line, the data lineand the TFT “T” is formed on the second substrate 50. A color filterlayer 34 including sub-color filters 34a and 34b is formed on the blackmatrix 32. Each sub-color filter 34a and 34b corresponds to the pixelregion “P₁” and “P₂.” A liquid crystal layer 90 is driven by a lateralelectric field 95 between the common electrode 58 and the pixelelectrode 72.

[0011]FIG. 2 is a schematic plan view of an array substrate for anin-plane switching mode liquid crystal display device according to therelated art. In FIG. 2, a gate line 54 is formed on a substrate 50 and adata line 68 crosses the gate line 54 to define a pixel region “P.” Inaddition, a common line 56 parallel to the gate line 54 crosses thepixel region “P.” A thin film transistor (TFT) “T” including a gateelectrode 52, a semiconductor layer 62, a source electrode 64 and adrain electrode 66 is connected to the gate line 54 and the data line68. The gate electrode 52 and the source electrode 64 are connected tothe gate line and the data line 68, respectively. Common electrodes 58are formed in the pixel region “P.” The common electrodes 58perpendicularly extend from the common line 56 and are parallel to eachother. Pixel electrodes 72 alternate with and are parallel to the commonelectrodes 58.

[0012]FIG. 3A is a schematic view showing an OFF state of a liquidcrystal layer of an in-plane switching mode liquid crystal displaydevice according to the related art and FIG 3B is a schematic viewshowing an ON state of liquid crystal molecules of an in-plane switchingniode liquid crystal display device according to the related art.

[0013] In FIG. 3A, a liquid crystal molecule 90a keeps an initial statewhen a voltage is not applied to a common electrode 58 and a pixelelectrode 72. As shown in FIG. 3B, when a voltage is applied to thecommon electrode 58 and the pixel electrode 72, a lateral electric field95 is generated between the common electrode 58 and the pixel electrode72. The liquid crystal molecule 90a rotates according to the lateralelectric field 95 and is re-arranged to have an angle with respect tothe lateral electric field 95. When the liquid crystal molecule 90amakes an angle of 45° with respect to the lateral electric field 95,transmittance of the liquid crystal layer is maximized. However, if ahigher voltage is applied, the liquid crystal molecule 90a rotates andmakes an angle less than 45° with respect to the lateral electric field95. As a result, transmittance is reduced again.

[0014]FIG. 4 is a V-T curve showing transmittance property according tovoltage of an in-plane switching mode liquid crystal display deviceaccording to the related art. As shown in FIG. 4, assuming that amaximum applied voltage is 10V, transmittance has the maximum value at6V. As the applied voltage increases over 6V, a transmittance curvedeclines. When a voltage over 6V is applied, a liquid crystal moleculeis re-arranged nearly parallel to a lateral electric field. Accordingly,the liquid crystal molecule makes an angle less than 45° with respect tothe lateral electric field and transmittance is reduced.

[0015]FIG. 5 is a graph showing a viewing angle property of an in-planeswitching mode liquid crystal display device according to the relatedart. As shown in FIG. 5, viewing angle property is not symmetricalaccording to viewpoint such as up-and-down and right-and-left of aliquid crystal panel. Accordingly, a stable wide viewing angle is notobtained and a color shift, such as yellow shift and blue shift,severely occurs. These disadvantages deteriorate display quality of anIPS mode LCD device.

SUMMARY OF THE INVENTION

[0016] Accordingly, the present invention is directed to a liquidcrystal display device and a method of fabricating a liquid crystaldisplay device that substantially obviates one or more of the problemsdue to limitations and disadvantages of the related art.

[0017] An object of the present invention is to provide an in-planeswitching mode liquid crystal display device having stable transmittanceproperty with high applied voltage and a method of fabricating the same.

[0018] Another object of the present invention is to provide an in-planeswitching mode liquid crystal display device where a common electrodeand a pixel electrode of “L” shape symmetrically face each other and amethod of fabricating the same.

[0019] Additional features and advantages of the invention will be setforth in the description which follows, and in part will be apparentfrom the description, or may be learned by practice of the invention.These and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

[0020] To achieve these and other advantages and in accordance with thepurpose of the present invention, as embodied and broadly described, anarray substrate for an in-plane switching mode liquid crystal displaydevice comprises a substrate; a thin film transistor on the substrate; agate line connected to the transistor; a data line crossing the gateline and connected to the transistor, the crossed data line and gateline defining boundaries of a pixel region; a pixel electrode disposedin the pixel region connected to the transistor, the pixel electrodeincluding at least one vertical portion and a plurality of horizontalportions; and a common electrode disposed in the pixel region, thecommon electrode including at least two horizontal portions and aplurality of horizontal portions, wherein the vertical portion of thepixel electrode is disposed between the vertical portions of the commonelectrode, and the horizontal portions of the common electrode cross thevertical portion of the pixel electrode.

[0021] In another aspect, a method of fabricating an array substrate foran in-plane switching mode liquid crystal display device comprisesforming a gate line on a substrate; forming a data line crossing thegate line, the crossed data line and gate line defining boundaries of apixel region; forming a thin film transistor; forming a pixel electrodein the pixel region to include a vertical portion and a plurality ofhorizontal portions; and forming a common electrode in the pixel regionto include at least two vertical portions and a plurality of horizontalportions, wherein the pixel electrode, data line and gate electrode areconnected to the thin film transistor, wherein the vertical portion ofthe pixel electrode is disposed between the vertical portions of thecommon electrode, and wherein the horizontal portions of the commonelectrode cross the vertical portion of the pixel electrode.

[0022] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory and are intended to provide further explanation of theinvention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention and together with the description serve to explain theprinciples of the invention. In the drawings:

[0024]FIG. 1 is a schematic cross-sectional view of an in-plane modeliquid crystal display device according to the related art;

[0025]FIG. 2 is a schematic plan view of an array substrate for anin-plane switching mode liquid crystal display device according to therelated art;

[0026]FIG. 3A is a schematic view showing an OFF state of a liquidcrystal layer of an in-plane switching mode liquid crystal displaydevice according to the related art;

[0027]FIG. 3B is a schematic view showing an ON state of liquid crystalmolecules of an in-plane switching mode liquid crystal display deviceaccording to the related art;

[0028]FIG. 4 is a V-T curve showing transmittance property according tovoltage of an in-plane switching mode liquid crystal display deviceaccording to the related art;

[0029]FIG. 5 is a graph showing a viewing angle property of an in-planeswitching mode liquid crystal display device according to the relatedart;

[0030]FIG. 6 is a schematic plan view of an array substrate for anin-plane switching mode liquid crystal display device according to afirst embodiment of the present invention;

[0031]FIG. 7A is a schematic plan view showing an OFF state of a liquidcrystal layer of an in-plane switching mode liquid crystal displaydevice according to the first embodiment of FIG. 6;

[0032]FIG. 7B is a schematic plan view showing an ON state of liquidcrystal molecules of an in-plane switching mode liquid crystal displaydevice according to the first embodiment of FIG. 6;

[0033]FIG. 8 is a schematic plan view showing an alignment state ofliquid crystal molecules of an in-plane switching mode liquid crystaldisplay device according to the first embodiment of FIG. 6;

[0034]FIG. 9 is a schematic cross-sectional view showing an alignmentstate of liquid crystal molecules and transmittance of an in-planeswitching mode liquid crystal display device according to a firstembodiment of the present invention;

[0035]FIG. 10 is a V-T curve showing transmittance property according tovoltage of an in-plane switching mode liquid crystal display deviceaccording to the first embodiment of the present invention;

[0036]FIG. 11 is a schematic plan view showing a common electrode and apixel electrode for an in-plane switching mode liquid crystal displaydevice according to a second embodiment of the present invention;

[0037]FIG. 12 is a schematic plan view showing a common electrode and apixel electrode for an in-plane switching mode liquid crystal displaydevice according to a third embodiment of the present invention;

[0038]FIG. 13 is a schematic plan view showing a common electrode and apixel electrode for an in-plane switching mode liquid crystal displaydevice according to a fourth embodiment of the present invention;

[0039]FIGS. 14A to 14E are schematic cross-sectional views taken along aline “XIV-XIV” of FIG. 6 showing a fabricating process of an arraysubstrate for an in-plane switching mode liquid crystal display deviceaccording to the first embodiment of the present invention; and

[0040]FIGS. 15A to 15E are schematic cross-sectional views, taken alonga line “XV-XV” of FIG. 6 showing a fabricating process of an arraysubstrate for an in-plane switching mode liquid crystal display deviceaccording to the first embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Reference will now be made in detail to the preferred embodimentsof the present invention, an example of which is illustrated in theaccompanying drawings.

[0042]FIG. 6 is a schematic plan view of an array substrate for anin-plane switching mode liquid crystal display device according to afirst embodiment of the present invention. In FIG. 6, a gate line 104 isdisposed along a first direction on a substrate 100 and a data line 120is disposed along a second direction. The data line 120 crosses the gateline 104 to define a pixel region “PA.” A thin film transistor (TFT) “T”including a gate electrode 102, a semiconductor layer 112, a sourceelectrode 116 and a drain electrode 118 is formed in the pixel region“PA.” A common electrode 106 alternates with a pixel electrode 126 alongthe first and second directions in the pixel region “PA.” The commonelectrode 106 and the pixel electrode 126 having a shape of character“L” symmetrically face each other along a diagonal direction of thepixel region “PA.” Accordingly, the pixel region “PA” may be dividedinto a plurality of domains “A₁” to “A₈” each having a rectangularshape.

[0043] The common electrode 106 includes a first vertical portion 106a,a second vertical portion 106b, a first horizontal portion 106c and asecond horizontal portion 106d. The first and second vertical portions106a and 106b are disposed at both sides of the pixel region “PA” andparallel to the data line 120, and the first and second horizontalportions 106c and 106d cross and combine the first and second verticalportions 106a and 106b. The pixel electrode 126 includes a verticalportion 126a, a first horizontal portion 126b, a second horizontalportion 126c and a third horizontal portion 126d. The vertical portion126a is parallel to and spaced apart from the first and second verticalportions 106a and 106b of the common electrode 106, and the first tothird horizontal portions 126b to 126d cross the vertical portion 126a.The first and second horizontal portions 106c and 106d of the commonelectrode 106 alternate with and are spaced apart from the first tothird horizontal portions 126b to 126d of the pixel electrode 126.

[0044] A common line “c” connects the common electrode 106 and aneighboring common electrode (not shown) for supplying a common voltageto all common electrodes in a liquid crystal panel. The third horizontalportion 126d of the pixel electrode 126 overlaps the gate line 104 todefine a storage capacitor “C_(ST).”

[0045] The common electrode 106 and the pixel electrode 126 divide thepixel region “PA” into a plurality of domains “A₁” to “A₈.” Electricfields 300a and 300b generated between the common electrode 106 and thepixel electrode 126 in each domain may have symmetric directions havingangles of about 135° and about 45° with respect to the horizontalportions 106c, 106d, 126b, 126c and 126d of the common electrode 106 andthe pixel electrode 126. Accordingly, a plurality of domains “A₁” to“A₈” having symmetric alignment directions are formed in one pixelregion “PA” due to the symmetric electric fields 300a and 300b.Moreover, deterioration, such as color shift, is prevented due to anoptical compensation and an LCD device having high display quality andwide viewing angle is obtained. In addition, since the electric fields300a and 300b have diagonal directions, the LCD device has hightransmittance even when a relatively high voltage is applied to thecommon electrode 106 and the pixel electrode 126.

[0046] In FIG. 6, the pixel region “PA” is divided into 8 domains. Whilenot shown in figures, the number of domains may be adjusted according tothe number of vertical and horizontal portions of the common electrodeand the pixel electrode in alternative embodiments.

[0047]FIG. 7A is a schematic plan view showing an OFF state of a liquidcrystal layer of an in-plane switching mode liquid crystal displaydevice, and FIG. 7B is a schematic plan view showing an ON state ofliquid crystal molecules of an in-plane switching mode liquid crystaldisplay device.

[0048] In FIG. 7A, a common electrode 106 and a pixel electrode 126having an “L” shape face each other and are symmetrically disposed alonga diagonal direction of a pixel region. The common electrode 106 hasfirst and second vertical portions 106a and 106b and a first horizontalportion 106c. The pixel electrode 126 has a vertical portion 126a and afirst horizontal portion 126b. Liquid crystal molecules 200 keep aninitial state when a voltage is not applied to the common electrode 106and the pixel electrode 126.

[0049] In FIG. 7B, when a voltage is applied to the common electrode 106and the pixel electrode 126, first and second electric fields 300a and300b are generated between the common electrode 106 and the pixelelectrode 126 and liquid crystal molecules 200 are re-arranged along thefirst and second electric fields 300a and 300b. As an applied voltageincreases, the liquid crystal molecules 200 rotate further such that along axis of a liquid crystal molecule coincides with a direction of thegenerated electric field. However, the first electric field 300a makesan angle of about 135° with respect to the first horizontal portion 126bof the pixel electrode 126, and the second electric field 300b makes anangle of about 45° with respect to the first horizontal portion 126b ofthe pixel electrode 126. Accordingly, the liquid crystal molecules 200are re-arranged to have angles of about 135° and about 45° with respectto the first horizontal portion 126b of the pixel electrode 126 evenwhen a higher voltage is applied. As a result, transmittance is notreduced when the higher voltage is applied and keeps the maximum value.

[0050]FIG. 8 is a schematic plan view showing an alignment state ofliquid crystal molecules of an in-plane switching mode liquid crystaldisplay device, and FIG. 9 is a schematic cross-sectional view showingan alignment state of liquid crystal molecules and transmittance of anin-plane switching mode liquid crystal display device. FIG. 8 is takenfrom a portion “S” of FIG. 6 and FIG. 9 is taken along line “IX-IX” ofFIG. 8. FIGS. 8 and 9 are obtained by computer simulation.

[0051] As shown in FIG. 8, when a voltage is applied, a pixel region maybe divided into first to fourth domains “A₁” to “A₄” by first and secondelectric fields 300a and 300b. The first electric field 300a induced inthe second and third domains “A₂” and “A₃” has an angle of about 135°with respect to a first horizontal portion 126a (of FIG. 7B) of thepixel electrode 126 (of FIG. 7B), while the second electric field 300binduced in the first and fourth domains “A₁” and “A₄” has an angle ofabout 45° with respect to a first horizontal portion 126a (of FIG. 7B)of the pixel electrode 126 (of FIG. 7B). Accordingly, liquid crystalmolecules 200 (of FIG. 7B) are symmetrically re-arranged in the first tofourth domains “A₁” to “A4,” thereby preventing a color shift due tooptical compensation.

[0052] As shown in FIG. 9, when a voltage is applied, transmittancecurve 350 has maximum value in the first and second domains “A1” and“A2” except for portions corresponding to the common electrode 106 (ofFIG. 7B) and the pixel electrode 126 (of FIG. 7B).

[0053]FIG. 10 is a V-T curve showing transmittance property according tovoltage of an in-plane switching mode liquid crystal display device. Asshown in FIG. 10, transmittance curve 360 increases according to avoltage applied to a common electrode and a pixel electrode. When avoltage of about 6V is applied, the transmittance curve has a maximumvalue of about 100%. In addition, the transmittance curve does notdecrease but keeps the maximuni value of about 100% even when a voltagehigher than about 6V is applied. Accordingly, a voltage higher than acritical value, for example, about 6V, may be used for an IPS mode LCDdevice so that images of high brightness and high display quality can bedisplayed through the IPS mode LCD device.

[0054]FIG. 11 is a schematic plan view showing a common electrode and apixel electrode for an in-plane switching mode liquid crystal displaydevice according to a second embodiment of the present invention, andFIG. 12 is a schematic plan view showing a common electrode and a pixelelectrode for an in-plane switching mode liquid crystal display deviceaccording to a third embodiment of the present invention.

[0055] In FIGS. 11 and 12, a common electrode 106 alternates with apixel electrode 126 along the first and second directions in a pixelregion. The common electrode 106 and the pixel electrode 126 having ashape of character “L” symmetrically face each other along a diagonaldirection of the pixel region. Accordingly, the pixel region may bedivided into a plurality of domains “A1” to “A8” having a rectangularshape.

[0056] The common electrode 106 includes a first vertical portion 106a,a second vertical portion 106b, a first horizontal portion 106c and asecond horizontal portion 106d. The first and second vertical portions106a and 106b are disposed at both sides of the pixel region, and thefirst and second horizontal portions 106c and 106d cross and combine thefirst and second vertical portions 106a and 106b. The pixel electrode126 includes a vertical portion 126a, a first horizontal portion 126b, asecond horizontal portion 126c and a third horizontal portion 126d. Thevertical portion 126a is parallel to and spaced apart from the first andsecond vertical portions 106a and 106b of the common electrode 106, andthe first to third horizontal portions 126b to 126d cross the verticalportion 126a.

[0057] The vertical portion 126a of the pixel electrode 126 alternateswith the first and second vertical portions 106a and 106b of the commonelectrode 106. The first to third horizontal portions 126b to 126d ofthe pixel electrode 126 alternate with the first and second horizontalportions 106c and 106d of the common electrode 106.

[0058] In each of the plurality of domains “A1” to “A8” having arectangular shape, an electric field is induced between the commonelectrode 106 and the pixel electrode 126 along a diagonal direction ofthe rectangular shape. Distance between the common electrode 106 and thepixel electrode 126 along the diagonal direction varies according topositions of the common electrode 106 and the pixel electrode 126. Thedistance has a maximum value between a first edge region “F1” of thecommon electrode 106 and a second edge region “F2” of the pixelelectrode 126 in each domain. The first edge region is a crossing regionof the vertical portions 106a and 106d and the horizontal portions 106band 106c of the common electrode 106. In addition, the second edgeregion “F2” is a crossing region of the vertical portion 126a and thehorizontal portions 126b, 126c and 126d of the pixel electrode 126.

[0059] Electric field intensity is inversely proportional to a square ofa distance between charges (source of electric field). Thus, as thedistance between charges decreases, the electric field intensityincreases and liquid crystal molecules respond to the electric fieldfaster. In the second and third embodiments, an auxiliary commonelectrode is formed at the first edge region “F1,” and an auxiliarypixel electrode is formed at the second edge region “F2.” The auxiliarycommon electrode extends from the common electrode 106 and fills thefirst edge region “F1,” and the auxiliary pixel electrode extends fromthe pixel electrode 126 and fills the second edge region “F2.” As aresult, the distance “L” between the first and second edge regions “F1”and “F2” is reduced and the electric field intensity increases.Accordingly, a response time of the liquid crystal molecules is reducedand quality of the IPS mode LCD device is improved. An outer side of theauxiliary common electrode and the auxiliary pixel electrode has astraight shape in the second embodiment of FIG. 11, and an outer side ofthe auxiliary common electrode and the auxiliary pixel electrode has around shape in the third embodiment of FIG. 12.

[0060]FIG. 13 is a schematic plan view showing a common electrode and apixel electrode for an in-plane switching mode liquid crystal displaydevice according to a fourth embodiment of the present invention.

[0061] As shown in FIG. 13, a common electrode 106 overlaps a pixelelectrode 126 with an intervening insulating layer at a crossing region“G” Accordingly, the common electrode 106 and the pixel electrode 126constitute an undesired capacitor and this undesired capacitor may causereduction of response speed of liquid crystal molecules. To reducecapacitance of the undesired capacitor, the common electrode 106 isformed such that a width of the crossing region “G” is less than that ofthe other regions. Similarly, the pixel electrode 126 is formed suchthat a width of the crossing region “G” is less than that of the otherregions. Therefore, capacitance of the crossing region “G” is reducedand response speed of liquid crystal molecules is increased so that highdisplay quality can be obtained.

[0062]FIGS. 14A to 14E are schematic cross-sectional views taken alongline “XIV-XIV” of FIG. 6 showing a fabricating process of an arraysubstrate for an in-plane switching mode liquid crystal display deviceaccording to the first embodiment of the present invention, and FIGS.15A to 15E are schematic cross-sectional views taken along a line“XV-XV” of FIG. 6 showing a fabricating process of an array substratefor an in-plane switching mode liquid crystal display device accordingto the first embodiment of the present invention.

[0063] In FIGS. 14A and 15A, a gate electrode 102 and a gate line 104are formed on a substrate 100 having a switching region “TA” and a pixelregion “PA” by depositing and patterning one of aluminum (Al) andaluminum (Al) alloy. The gate electrode 102 connected to the gate line104 is disposed in the switching region “TA” and the gate line 104 isdisposed at one side of the pixel region “PA.” A common electrodeincluding vertical portions and horizontal portions is formed on thesubstrate 100 in the pixel region “PA.” While FIG. 15A shows only firstand second horizontal portions 106c and 106d of the common electrode,first and second vertical portions perpendicular to the gate line 104are also formed on the substrate 100, at both sides of the pixel region“PA.” While not shown in FIG. 15A, the common electrode in the pixelregion “PA” is connected to another common electrode in adjacent pixelregion.

[0064] The gate line may include aluminum (Al) to reduce resistance andprevent signal delay. Since pure aluminum (Al) is susceptible physicallyand chemically, defects, such as pinholes and hillocks, are apt tooccur. Accordingly, a protection layer including an additional metallicmaterial such as chromium (Cr) and molybdenum (Mo).

[0065] In FIGS. 14B and 15B, a gate insulating layer 110 is formed on anentire surface of the substrate 100 having the gate electrode 102, thegate line 104 and the common electrode 106 (of FIG. 6) by depositing oneof an inorganic insulating material such as silicon oxide (SiO₂) andsilicon nitride (SiNx). An active layer 112 and an ohmic contact layer114 are sequentially formed on the gate insulating layer 110 over thegate electrode 102 by depositing and patterning amorphous silicon(a-Si:H) and impurity-doped amorphous silicon (n+a-Si:H).

[0066] In FIGS. 14C and 15C, a source electrode 116 and a drainelectrode 118 are formed on the ohmic contact layer 114 by depositingand patterning one of a conductive metallic material, such as chromium(Cr), molybdenum (Mo), tungsten (W), titanium (Ti) and copper (Cu). Thesource and drain electrodes 116 and 118 are spaced apart from eachother. At the same time, a data line 120 is formed on the gateinsulating layer 110. The data line 120 is connected to the sourceelectrode 116 and crosses the gate line 104 to define the pixel region“PA.”

[0067] In FIGS. 14D and 15D, a passivation layer 122 is formed on anentire surface of the substrate 100 having the source electrode 116, thedrain electrode 118 and the data line 120 by depositing and patterningone of an organic insulating material such as benzocyclobutene (BCB) andacrylic resin having a relatively low dielectric constant. Thepassivation layer 122 has a drain contact hole 124 exposing the drainelectrode 118.

[0068] In FIGS. 14E and 15E, a pixel electrode 126 (of FIG. 6) is formedon the passivation layer 122 by depositing and patterning one of atransparent conductive material such as indium-tin-oxide (ITO) andindium-zinc-oxide (IZO). The pixel electrode 126 (of FIG. 6) isconnected to the drain electrode 118 through the drain contact hole 124.The pixel electrode 126 (of FIG. 6) may include vertical portions andhorizontal portions such as vertical portion 126a (of FIG. 6) and firstto third horizontal portions 126b to 126d. The third horizontal portion126d of the pixel electrode 126 (of FIG. 6) overlaps the gate line 104to constitute a storage capacitor “CST” with the passivation layer 122and the gate insulating layer 110.

[0069] The common electrode 106 (of FIG. 6) and the pixel electrode 126(of FIG. 6) divide the pixel region “PA” into a plurality of domainshaving a rectangular shape. In each of the plurality of domains, thecommon electrode 106 (of FIG. 6) and the pixel electrode 126 (of FIG. 6)have a shape of character “L” and symmetrically face each other along adiagonal direction of the pixel region “PA.” Electric fields generatedbetween the common electrode 106 (of FIG. 6) and the pixel electrode 126(of FIG. 6) in each domain may have symmetric directions having anglesof about 135° and about 45° with respect to the horizontal portions106c, 106d, 126b, 126c and 126d of the common electrode 106 (of FIG. 6)and the pixel electrode 126 (of FIG. 6). Accordingly, the plurality ofdomains having symmetric alignment directions are formed in one pixelregion “PA” due to the symmetric electric fields and deterioration suchas color shift is prevented due to an optical compensation. Moreover,since the electric fields have angles of about 135° and about 45° evenwhen a high voltage is applied, a stable transmittance property isobtained. Therefore, display quality and viewing angle of an IPS modeLCD device are improved.

[0070] An IPS mode LCD device according to embodiments of the presentinvention has several advantages. First, since a common electrode and apixel electrode having a shape of character “L” are symmetricallydisposed along a diagonal direction to face each other, liquid crystalmolecules are re-arranged along a direction having an angle of about135° and about 45° with respect to a horizontal portion of the commonelectrode and the pixel electrode even when a relatively high voltage isapplied. Thus, high brightness is obtained. Second, since a relativelyhigh voltage is used to drive the liquid crystal molecules, a distancebetween a common electrode and a pixel electrode increases so thataperture ratio can be improved. Third, a response speed is improved dueto increased electric field intensity resulting from an auxiliary commonelectrode and an auxiliary pixel electrode at edge regions. Fourth, aresponse speed is improved due to reduction of undesired capacitanceresulting from reduction of width of a common electrode and a pixelelectrode at a crossing region. Fifth, since one pixel region includes aplurality of symmetric domains, color shift is prevented due to opticalcompensation and stable wide viewing angle is obtained.

[0071] It will be apparent to those skilled in the art that variousmodifications and variations can be made in the liquid crystal displaydevice and method of fabricating the same of the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An array substrate for an in-plane switching modeliquid crystal display device, comprising: a substrate; a thin filmtransistor on the substrate; a gate line connected to the transistor; adata line crossing the gate line and connected to the transistor, thecrossed data line and gate line defining boundaries of a pixel region; apixel electrode disposed in the pixel region connected to thetransistor, the pixel electrode including at least one vertical portionand a plurality of horizontal portions; and a common electrode disposedin the pixel region, the common electrode including at least twovertical portions and a plurality of horizontal portions, wherein thevertical portion of the pixel electrode is disposed between the verticalportions of the common electrode, and the horizontal portions of thecommon electrode cross the vertical portion of the pixel electrode. 2.The array substrate according to claim 1, wherein the common electrodeand the pixel electrode symmetrically face each other along a diagonaldirection of the pixel region.
 3. The array substrate according to claim1, wherein the common electrode and the pixel electrode define aplurality of domains having a rectangular shape in the pixel region. 4.The array substrate according to claim 1, wherein the thin filmtransistor includes a gate electrode connected to the gate line, asource electrode connected to the data line, and a drain electrodespaced apart from the source electrode and connected to the pixelelectrode.
 5. The array substrate according to claim 1, wherein thecommon electrode includes first and second vertical portions disposed atopposing sides of the pixel region, and the plurality of horizontalportions of the common electrode connect the first and second commonvertical portions.
 6. The array substrate according to claim 5, whereinthe vertical portion of the pixel electrode is disposed between thefirst and second vertical portions of the common electrode, and theplurality of horizontal portions of the pixel electrode cross thevertical portion of the pixel electrode and are spaced apart from theplurality of horizontal portions of the common electrode.
 7. The arraysubstrate according to claim 6, wherein one of the plurality ofhorizontal portions of the pixel electrode overlaps the gate line todefine a storage capacitor.
 8. The array substrate according to claim 6,wherein the plurality of horizontal portions of the cominon electrodecross the vertical portion of the pixel region at a crossing region. 9.The array substrate according to claim 8, wherein a width of at leastone of the horizontal portions of the common electrode at the crossingregion is less than the width of the at least one of the horizontalportions of the common electrode at other regions, and a width of thevertical portion of the pixel region at the crossing region is less thanthe width of the vertical portion of the pixel electrode at otherregions.
 10. The array substrate according to claim 6, furthercomprising an auxiliary common electrode portion at a crossing region ofone of the first and second vertical portions of the common electrodeand one of the plurality of horizontal portions of the common electrode.11. The array substrate according to claim 10, wherein an outer side ofthe auxiliary common electrode portion has one of a straight shape and around shape.
 12. The array substrate according to claim 6, furthercomprising an auxiliary pixel electrode portion at a crossing region ofthe vertical portion of the pixel electrode and one of the plurality ofhorizontal portions of the pixel electrode.
 13. The array substrateaccording to claim 12, wherein an outer side of the auxiliary pixelelectrode portion has one of a straight shape and a round shape.
 14. Amethod of fabricating an array substrate for an in-plane switching modeliquid crystal display device, comprising: forming a gate line on asubstrate; forming a data line crossing the gate line, the crossed dataline and gate line defining boundaries of a pixel region; forming a thinfilm transistor; forming a pixel electrode in the pixel region toinclude at least one vertical portion and a plurality of horizontalportions; and forming a common electrode in the pixel region to includeat least two vertical portions and a plurality of horizontal portions,wherein the pixel electrode, data line, and gate electrode are connectedto the thin film transistor, wherein the vertical portion of the pixelelectrode is disposed between the vertical portions of the commonelectrode, and wherein the horizontal portions of the common electrodecross the vertical portion of the pixel electrode.
 15. The methodaccording to claim 14, wherein the gate line is formed of the same layerand the same material as the common electrode.
 16. The method accordingto claim 14, wherein the plurality of horizontal portions of the commonelectrode are connected between the vertical portions of the commonelectrode.
 17. The method according to claim 16, wherein the pluralityof horizontal portions of the pixel electrode crossing the verticalportion of the pixel electrode and are spaced apart from the pluralityof horizontal portions of the common electrode.
 18. The method accordingto claim 17, wherein the plurality of horizontal portions of the commonelectrode cross the vertical portion of the pixel electrode at acrossing region.
 19. The method according to claim 18, wherein a widthof at least one of the horizontal portions of the common electrode atthe crossing region is less than the width of the at least one of thehorizontal portions of the common electrode at other regions, and awidth of the vertical portion of the pixel region at the crossing regionis less than the width of the vertical portion of the pixel electrode atother regions.
 20. The method according to claim 17, further comprisingforming an auxiliary common electrode portion at a crossing region ofone of the first and second vertical portions of the common electrodeand one of the plurality of horizontal portions of the common electrode.21. The method according to claim 20, wherein an outer side of theauxiliary common electrode portion has one of a straight shape and around shape.
 22. The method according to claim 17, further comprisingforming an auxiliary pixel electrode portion at a crossing region of thevertical portion of the pixel electrode and one of the plurality ofhorizontal portions of the pixel electrode.
 23. The method according toclaim 22, wherein an outer side of the auxiliary pixel electrode portionhas one of a straight shape and a round shape.